Apparatus for forming a cored concrete slab

ABSTRACT

An apparatus and method for forming cored concrete slab utilizing an elongated fixed mold for forming the opposite sides and bottom surface of the slab. A concrete depositing and core forming assembly moves longitudinally over the mold, the assembly including a plurality of elongated core forming mandrels and a hopper which deposits a first layer of concrete in the mold generally to the top of the mandrels. A length of metal mesh is provided having its free end attached at one end of the mold, the mesh being coiled on a reel mounted on the assembly which lays the mesh over the mandrels and the first layer, applying tension thereto, as the assembly moves toward the other end of the mold. Another hopper is mounted on the assembly which deposits a second layer of concrete over the first layer and mesh.

Yost

ited States Patent APPARATUS FOR FORMING A CORED CONCRETE SLAB Robert L.Yost, Decatur, Ind.

Joseph J. Dues, Dayton, Ohio Oct. 28, 1968 Inventor:

Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS 8/1964 Kalns ..25/41.5 A 4/1965Roth et a1 ..25/41 J 2,663,063 12/1953 Van Loon ..25/4l.5 A

Primary Examiner-.1. Spencer Overholser Assistant ExaminerDeWalden W.Jones Attorney1-Iood, Gust, Irish & Lundy ABSTRACT An apparatus andmethod for forming cored concrete slab utilizing an elongated fixed moldfor forming the opposite sides and bottom surface of the slab. Aconcrete depositing and core forming assembly moves longitudinally overthe mold, the assembly including a plurality of elongated core formingmandrels and a hopper which deposits a first layer of concrete in themold generally to the top of the mandrels. A length of metal mesh isprovided having its free end attached at one end of the mold, the meshbeing coiled on a reel mounted on the assembly which lays the mesh overthe mandrels and the first layer, applying tension thereto, as theassembly moves toward the other end of the mold. Another hopper ismounted on the assembly which deposits a second layer of concrete overthe first layer and mesh.

15 Claims, 8 Drawing Figures PATENTEUMAR I 1912 v 3, 647, 308

sum 1 BF 6 INVENTOFZ Rosem L. Yosr be. Homo, Gus'r, lmsu Lunov AHornevsPATENTEDMAR 7 1972 SHEET 2 BF 6 INVENTQR QOBERT LYosT bu H000 ATfor-neysAPPARATUS FOR FORMING A CORED CONCRETE SLAB BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates generally toapparatus and methods of forming reinforced concrete structuralelements, and more particularly to an apparatus and method for forming acored concrete slab from low slump concrete.

2. Description of the Prior Art Prestressed reinforced concrete beams,slabs, panels and other structural elements are extensively employed inthe construction industry. Many of such elements are of the cored type,i.e., having cavities or cores therein for reducing the overall weight.

Such cored concrete structural elements are commonly formed by one oftwo different processes. The first process, employs a concrete mixturehaving no slump. This mixture is pressure formed into the desired shape.In one form of apparatus utilizing no slump concrete, an elongatedstationary mold is employed which forms the sides and bottom surface ofthe element. An extruding device moves along the mold carrying a topplate which completes the mold cavity, and the relatively dry concretemixture is forced into the cavity by rotating augers which alsorespectively form the cores in the product. In another apparatusutilizing no slump concrete an extruding assembly moves over a bedsuccessively depositing three layers of relatively dry concrete mix,each layer being compacted by reciprocating tamping devices. The middlelayer surrounds a plurality of reciprocating mandrels which form thecores, and the sides of the slab are formed by a slip form device whichadvances with the assembly. Both of the abovedescribed types ofapparatus for performing the dry process possess certain disadvantages.One such disadvantage is that it has not been possible to incorporateinserts, such as electrical junction boxes, conduits and the like, intoslabs formed in this manner.

In the second method of forming prestressed, cored concrete structuralelements, concrete having a low slump is poured in the mold, cured andremoved therefrom. There is a preference in the industry for usingconcrete having a low slump rather than concrete having no slump,particularly where it is desired to include various types of inserts inthe product. In one comparatively simple form of apparatus employing lowslump concrete, a stationary mold is provided which forms the sides andbottom surface of the product. Elongated inflated mandrels arepositioned in the mold and the relatively fluid or wet concrete is thenpoured into the mold covering the mandrels. After curing, the mandrelsare deflated and removed leaving the cores in the product. In anothertype of apparatus employing low slump concrete, referred to as a slipform machine, an assembly is moved over a bed. The slip form machineforms the sides of the product; the bed forms the bottom surface of theslab. This assembly also carries a plurality of elongated mandrels orcore tubes which form the cores in the product, the relatively wetconcrete being poured over the mandrels into the mold cavity formed bythe slip form machine and the stationary bed. The speed of operation ofthe slip form machine is necessarily limited by the fact that the movingassembly carries a portion of the mold and thus can travel only as fastas the concrete cures so as to be self-supporting.

SUMMARY OF THE INVENTION It is desired to provide an apparatus andmethod for forming a prestressed, cored concrete slab employing lowslump concrete which incorporates all of the advantages of such aprocess.

In accordance with the broader aspects of the invention, alongitudinally elongated hold is provided for forming the opposite sidesand bottom surface of the slab. Means are provided for progressivelylaying a layer of cementitious material in the mold and including meansdisposed over the mold for receiving cementitious material in relativelyfluid form and depositing the same in the mold, and means are providedfor relatively longitudinally moving the depositing means with respectto the mold in the direction of elongation thereof. A plurality ofelongated mandrels are provided disposed in the mold in spaced, parallelrelationship and extending in the direction of relative movement forforming the longitudinally extending cores in the slab, the mandrelshaving spaced opposite ends and having portions intermediate their endsdisposed under the depositing means. Means are provided for attachingthe leading ends of the mandrels which face in the direction of relativemovement to the laying means so that the mandrels are relatively movedwith the depositing means. In the preferred embodiment, the layer ofcementitious material is deposited to a level generally even with thetops of the mandrels and an elongated length of mesh reinforcingmaterial is provided having its free end attached to the mold, thelaying means laying the mesh, under tension, over the previouslydeposited layer, the laying means including means for depositing asecond layer of cementitious material in relatively fluid form over thefirst layer and mesh.

It is accordingly an object of the invention to provide improvedapparatus for forming a cored concrete product.

Another object of the invention is to provide an improved apparatusemploying concrete having a low slump, in contrast to no slump, forforming a prestressed, cored concrete product.

A further object of the invention is to provide an improved method forforming a cored concrete slab from concrete having a low slump incontrast to no slump.

The above-mentioned and other features and objects of this invention andthe manner of attaining them will become more apparent and the inventionitself will be best understood by reference to the following descriptionof an embodiment of the invention taken in conjunction with theaccompanying drawings, wherein;

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary view inperspective, partly broken away, illustrating the apparatus of theinvention;

FIG. 2 is a top view of the apparatus illustrated in FIG. 1;

FIG. 3 is a side view of the apparatus illustrated in FIG. 1, partlybroken away;

FIG. 4 is a fragmentary cross-sectional view, partly schematic, takengenerally along the line 44 of FIG. 2;

FIG. 5 is a fragmentary cross-sectional view, taken generally along theline 5-5 of FIG. 2;

FIG. 6 is a generally schematic diagram showing the propulsion system ofthe apparatus;

FIG. 7 is a fragmentary view in perspective, partly in cross section,useful in explaining the method of the invention, and furtherillustrating certain features of the apparatus; and

FIG. 8 is a fragmentary cross-sectional view taken along the line 8-8 ofFIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT The Apparatus Referring now tothe drawings, the apparatus of the invention, generally indicated at 10,comprises a mold assembly 12 for forming the parallel opposite sides andbottom surface of slab l4, and an assembly 16 which travels on the molddepositing cementitious material therein, forming the core openings inthe slab, and finishing the top surface as its forward movement in thedirection shown by the arrow 18 progresses.

Mold 12, only a short section of which is shown, but which may beseveral hundred feet in length, comprises a bed 20 supported upon asupporting surface 22, such as the ground, by a plurality oflongitudinally spaced-apart support elements 24. Bed 20 may haveconduits 26 formed therein for circulating a heating medium, such asheated oil, in order to accelerate the curing of the slab in the mold. Apair of side mold elements 28, 30 are provided on the opposite sides ofbed 20 and extend longitudinally the entire length thereof. Side moldelements 28 and 30 have rails 32 and 34 formed on their upperextremities for supporting the assembly 16 for longitudinal movementwith respect to the mold 12. Side mold elements 28 and 30 are supportedupon the supporting surface 22 by a plurality of spaced-apart,vertically adjustable supports 36, and are adapted to be verticallyraised and lowered between upper and lower positions by a plurality ofconventional hydraulic jacks 38. In their upper positions, side moldelements 28. and 30 extend upwardly above the upper flat surface 40 ofbed 20. The inner surfaces 42 and 44 of side mold elements 28 and 30thus define a mold cavity having an open top. The elements 28, 30 withupper surface 40 of base form the opposite parallel sides and bottomsurface of the slab 14. In the lower positions of side mold elements 28and 30, rails 32 and 34 are flush with the upper surface 40 of base 20,or lower, thereby to assist in the removal of the slab 14 from the moldcavity and to permit transverse sawing of the elongated slab 14 in themold into shorter elements of desired length by a conventional concretesawing apparatus (not shown).

The assembly 16 comprises a supporting frame 46 supported on the rails32 and 34 of the side mold elements 28 and for longitudinal movementthereon by means of a forward pair of wheels 48 and 50 and a rear pairof wheels 52 and 54. The forward pair of wheels 48 r and 50 arerespectively mounted on an axle 56 and the rear pair of wheels 52 and 54are likewise mounted on an axle 58, axles 56 and 58 being mounted onframe 46, as shown.

The assembly 16 is moved longitudinally over the mold 12 in thedirection shown by the arrow 18. The assembly 16 is guided to move onthe rails 32 and 34 by the guides 47. The guides 47 are located at eachcorner of the frame 46 and engage the facing surfaces 42 and 44 ofelements 28 and 30.

The wheels 48, 50, 52 and 54 are driven by the propulsion system shownin FIG. 6. A suitable electric motor 60 is mounted on frame 46 anddrives a conventional hydraulic pump 62 through a conventional beltdrive 64. Pump 62 receives hydraulic fluid from hydraulic tank 66through supply line 68. Hydraulic pump 62 independently drives theforward pair of wheels 48 and 50, and the rear pair of wheels 52 and 54,respectively, through conventional hydraulic motors 70 and 72. Pump 62is connected to the forward hydraulic motor 70 by pressure line 74,hydraulic motor 70 having a discharge line 76 which is returned to thetank 66. Pump 62 likewise drives the hydraulic motor 72 through pressureline 78, motor 72 having discharge line 80 which is returned to the tank66.

The forward hydraulic motor 70 drives a suitable gearbox 82 Y 124 whichrespectively drive rear wheels 52, 54 through drive chains 126 and 128,driving sprockets 130, 132 thereon.

Motor may be energized by suitable flexible cables, or more preferablyby a conventional third rail and sliding contact system (not shown).Suitable motor controls 134 are provided for controlling the speed ofmotor 60 and thus the linear speed at which the assembly 16 moves in thedirection 18. Suitable catwalks 136 are supported on frame 46 for theoperator and provide access to the motor controls 134.

An elongated hopper 138 is mounted on frame 46 and extends transverselythereacross over the mold 12 for depositing cementitious material in themold cavity to form a first layer 140 therein as the assembly 16 movesforwardly in the direction 18. Hopper 138 has an open upper end 142 forreceiving the cementitious material, and forward and rear sidewalls 144and146 having converging lower extremities 148 and 150 which define anelongated, transversely extending discharge opening 152 for depositingthe cementitious material in the mold over the top surface 40 of base20. An elongated force feeding and distributing auger 154 is positionedin hopper 138 adjacent opening 152. Auger 154 is selectively driven inopposite directions by means of a conventional hydraulic motor 156 whichdrives gearbox 158 which, in turn, drives auger 154 through drive chain160. Hopper 138 may be continuously filled with cementitious material bymeans of a conventional ready-mix truck (not shown) which moves alongthe side of the mold 12 as the assembly 16 moves forwardly in direction18 or by like means.

A plurality of elongated core-forming mandrels 162 are provided in themold cavity and extending in spaced, parallel relationship in thedirection of movement. Mandrels 162 are in the form of hollow metaltubes closed at their opposite ends 164, 166 and have elongated rodportions 170 and 171 secured to the mandrels 162 at their opposite ends,rod portions 170 and 171 respectively project beyond opposite ends 164and 166. The portions 170 which project forwardly from the forward orleading ends 164 of mandrels 162, which face toward the direction ofmovement 18, are connected to frame 46 for rotational movement bydownwardly extending brackets 172. It will thus be seen that portions ofmandrels 162 as adjacent their leading ends 164 extend under thedischarge opening 152 of hopper 138, the rear or trailing ends 166 ofmandrels 162 extending substantially rearwardly of the rear end 174 offrame 46. In a specific embodiment of the apparatus of the invention,mandrels 162 were each 30 feet long and extended 20 feet beyond rear end174 of frame 46.

It will thus be seen that the mandrels 162 are mounted for rotationalmovement about their longitudinal axes which extend between theirleading and trailing ends 164, 166, rod portions 170, 171 being coaxialtherewith, and leading ends 164 of mandrels 162 being pulled by brackets172 as the assembly 16 moves forwardly in direction 18, the trailingends 166 being unsupported by the-frame 46 and floating in the layer ofcementitious material so as to form the core openings therein. In orderto keep the mandrels 162 submerged in the cementitious material, of thelayer 140 and to keep the mandrels 162 generally parallel to the surface40, mandrels 162 are wholly or partially filled with liquid 176,preferably a mixture of water and alcohol, so that the weight ofmandrels 162 is such that the trailing ends 166 will not float upwardlyor sink from the aforementioned desired position in the layer 140.In apreferred embodiment, conventional electrically energized immersionheaters 178 are provided within mandrels 162 for heating the samethereby to accelerate curing of the cementitious material. Mandrels 162have a limited rotary oscillatory troweling motion imparted theretoabout their axes by the arrangement now to be described. Referringspecifically to FIG. 4, in the illustrated embodiment, one group 180 ofthe mandrels 162 respectively have ends 182 of lever members 184 securedto projecting portions of rods 168. The upper ends 166 of lever members184 are respectively pivotally connected together by members 188. Aconventional hydraulic cylinder 190 is provided having its rear endpivotally connected to a side of frame 46, as at 192, and having itspiston rod 194 connected to members 188, as at 196. It will thus be seenthat protractile movement of piston rod 194 of cylinder 190 will resultin movement of members 198 and levers 184 to the position shown indashed lines in FIG. 4, whereas retractile movement of piston rod 194will move members 188 and levers 184 to the position shown in solidlines. Thus, reciprocatory motion of piston rod 194 results inreciprocatory motion of members 188, as shown by the arrows 198, in turnresulting in rotary, oscillatory troweling motion of mandrels 162, asshown by the arrows 200. Suitable limit switches, schematically shown at202 and 204, respectively sense the two extremities of the reciprocatorymovement of members 188 and are coupled to a suitable solenoid reversingvalve 206 for controlling the reciprocatory action of hydraulic cylinder190. In the illustrated embodiment of the apparatus which incorporatesl2 mandrels 162, the mandrels are divided into two groups each havingthe rotary, oscillatory troweling motion imparted thereto by a cylinder190, as best seen in FIG. 2.

In the preferred embodiment of the assembly 16, mandrels 162 rotateabout one-fourth revolution, and hopper 138 is disposed and auger 154 isdriven so as to deposit layer 140 of cementitious material to a level sothat its upper surface 208 is substantially even with the tops of themandrels 162, as best seen in FIG. 8. In this connection, it will beobserved that the edge 150 of sidewall 146 of hopper 138 will provide abulldozing action to assist in depositing the layer 140 to the level208.

A plurality of vibrating devices 210 are disposed between mandrels 162and adjacent to side mold elements 28, 30, closely adjacent rear edge150 of discharge opening 152 of hopper 138, vibrating devices 210 beingfurther disposed adjacent the tops of mandrels 162, as best seen inFIGS. 3 and 5. Vibrating devices 210 are individually driven by variablespeed electric drive motors 212 mounted on frame element 214 forwardlyof front wall 144 of hopper 138, each motor 212 being connected to andsupporting its respective vibrating device 210 by conduit 216 enclosinga conventional flexible drive shaft. The vibrating devices 210 functionto continuously pack the cementitious material between the mandrels 162and side elements 28, 30 as it is deposited by the auger 154 from thehopper 138. The speeds of the drive motors 212 and thus of the vibratingdevices 210 are individually selectively controlled by speed controls218 mounted on control panel 220.

ln accordance with the invention, an elongated length of metal meshmaterial 222 is provided having a width slightly less than the width ofthe mold 12 between the side mold elements 28, 30. As will behereinafter more fully described, free end 224 of mesh 222 is initiallysecured to a member 226 which is mounted adjacent the rear or startingend 228 of mold 12. Mesh 222 extends forwardly over mandrels 162 and isaccommodated on and payed out by a reel 230 rotatably supported bymembers 232 extending upwardly from frame 46, reel 230 being disposedrearwardly of the hopper 138. Mesh 222 is trained around guide rollers234 which are respectively disposed in alignment with the spaces betweenthe mandrels 162, rollers 234 pressing the mesh 222 downwardly againstthe tops of mandrels 162 and into the top surface 208 of cementitiousmaterial layer 140 between the mandrels, as best seen in FIG. 8. Mesh222 is maintained in tension as the assembly 16 moves forwardly indirection 18 by means of a suitable brake device 236 acting upon reel230. It will thus be seen that as the forward movement of assembly 16progresses in direction 18, mesh 222 is laid, under tension, overcementitious material layer 140 and mandrels 162, being pressed into thetop surface 208 of layer 140 by roller 234.

A second elongated hopper 236 is mounted on extension portion 238 offrame 46 which extends rearwardly from the rear end 174, hopper 236extending transversely across mold 12 over mandrels 162, cementitiousmaterial 140 and mesh 222, and being similar in construction to hopper138. Hopper 236 has an upper open end 240, a lower discharge opening242, and a force feeding and distributing auger 244 therein adjacent thedischarge opening 242. Hopper 236 receives cementitious material and inconjunction with auger 244 deposits a second layer 246 over mandrels162, the first layer 140 and mesh 222, as best seen in FIG. 8. Auger 244is selectively driven in opposite directions by another hydraulic motor248 which drives gearbox 250, which, in turn, drives auger 244 through adrive chain 252.

Hopper 236 is preferably continuously filled by means of an elevatingauger 254 and an open trough 256 which in inclined upwardly fromadjacent the forward hopper 138 toward the rear hopper 236, as best seenin FIG. 3. Elevating auger 254 is driven by a conventional electricmotor 258 through a belt 260. Thus, by employing two separate chutesfrom a readymix truck or two separate like devices, one for depositingthe cementitious material into the hopper 138, and the other fordepositing cementitious material in the trough 256 for elevation byauger 254 and depositing in the rear hopper 236, both hoppers 138 and236 can be supplied with cementitious material.

The second layer 246 of cementitious material is compacted and its topsurface 262 is finished by a vibratory screed 264 supported on frameextension portion 238. Various inserts, hardware or the like (not shown)may be placed in slab 14 after the mesh has been laid on top of themandrels before the mandrels have been removed from the slab portion inwhich the inserts are desirably placed. Adjacent to side elements 28, 30and around such inserts, surface 262 must be finished by hand.

Ends 166 of mandrels 162 also may be secured to brackets 172 by means ofprojecting portions 171 of rods 168, both of the projecting portions 170and 171 being adapted to be removably rotatably mounted in brackets 172and removably connected to ends 182 of levers 184. With thisarrangement, when the apparatus 16 has advanced to the far end of moldl2, remote from the starting end 228, and a slab has been completed andthe resulting elongated slab has been sawed into shorter sections andthe sections removed, projecting ends 170 may be disconnected frombrackets 172 and levers 184, the assembly 16 can be turned end-for-end,and the projecting ends 171 can be connected to brackets 172 and ends182 of levers 184, thereby making ends 166 of mandrels 162 the leadingends. The assembly 16 may then be advanced back to the former startingend of the mold to form another slab, thus eliminating the necessity forconveying the entire assembly back to the starting end of the mold priorto forming another slab.

THE METHOD Prior to commencing motion of the assembly 16 on the rails 32and 34 of the side mold elements 28 and 30, transversely extending,longitudinally spaced-apart reinforcing strands 266 are placed in themold cavity, and longitudinally extending, transversely spaced-apartprestressing strands 268 are placed thereover and extending the lengthof the mold. Strands 268 having their ends 270 secured to member 226 andtheir other ends (not shown) suitably tensioned, as by the use ofappropriate hydraulic tensioning jacks. Transverse and longitudinallyextending reinforcing strands 266 and 268 are held in assembled relationand spaced from the top surface 40 of base 20 by conventional spacers272. Other hardware such asjunction boxes 274, window frames, conduitsand the like may also be positioned within the mold cavity if desired.Assembly 16 is positioned on rails 32 and 34 with trailing ends 166 ofmandrels 162 adjacent mold end 228, and end 224 of mesh 222 is securedto member 226. If desired, cementitious material may be placed by handin the mold rearwardly from the front hopper 138 to the level of thetops of the mandrels 162, and to the desired level 262 rearwardly of therear hopper 236. Rela-v tively fluid, wet cementitious material, forexample concrete having a low slump, is then deposited from a ready-mixtruck or like device in the hopper 138 and trough 256 and forwardmovement of the assembly 16 in the direction shown by the arrow 18 iscommenced. As the forward movement progresses, the bottom layer ofcementitious material is deposited by trough 138 and auger 154 to alevel substantially even with the tops of the mandrels 162, that layeris tamped between the mandrels and adjacent side elements 28, 30 byvibratory devices 210, the mesh 222 is payed out from the reel 230,under tension, and is pressed onto the tops of the mandrels 162 and intothe top surface 208 of layer 140 by rollers 234, the second layer 246 isdeposited over the mandrels 162, mesh 222 and the bottom layer 140 byhopper 236 and the auger 244, and that layer is compacted and its topsurface 262 finished by the vibratory screed 264.

It will be observed that the floating mandrels 162 have their leadingends 164 pulled forwardly in the direction 18 by the forward motion ofthe assembly 16 thereby forming the core openings in the resulting slab.The mesh 222 serves not only as reinforcing material in the finishedslab, but further, in combination with the cementitious layer 140,supports the top layer 246 of wet cementitious material so that the coreopenings formed by the advancing mandrels 162 do not collapse. It willbe observed that the rotary oscillatory motion imparted to the mandrels162 provides a troweling action for the interior surfaces of the coreopenings formed by the mandrels 162 as the mandrels advance in thedirection 18.

There are a number of factors which must be correlated in order to forma satisfactory slab. These include the linear rate of speed of theassembly 16 in direction 18, the formulation of the cementitiousmaterial used, including in one specific embodiment thecement-aggregate-sand ratio, the moisture content and curing time of theconcrete mixture, the consistency or slump of the mixture, which isapplied in wet or fluid form, the aggregate size and weight, and thesize of the mesh 222 which must support the upper cementitious layer 246in a wet condition. More particularly, the linear rate of speed, curingtime, consistency and mesh size must be correlated so that the coreopenings formed by the mandrels 162, as they advance forwardly indirection 18, do not collapse, and the-linear rate of speed, moisturecontent and curing time must further be correlated so that the requisitesmooth finish is formed on the top surface 262 by the vibratory screed264.

In a specific embodiment of the apparatus and method for forming slabs 8inches thick and 8 feet wide, 12 mandrels respectively 30 feet long andhaving a 6-inch outside diameter were employed. A concrete mix having aslump from about 1 inch to about 2 inches is employed, preferably usinga formula comprising from about 1,000 lbs. to about 1,300 lbs. of No. 9stone; from about 1,700 lbs. to about 2,000 lbs. of No. 14 sand; fromabout 650 lbs. to about 760 lbs. of high early cement; from about 18 toabout 25 ounces of a water dispersing agent (100N, as sold by MasterBuilders); and from about 30 to about 40 gallons of water (correctingfor moisture in gravel and sand, humidity, etc.). Using a formula withinthis range, the assembly 16 can be moved at a linear forward speedwithin the range from about 1 foot per minute to about 6 feet perminute.

Particularly satisfactory results have been provided with a linearforward speed of about 2 feet per minute and a formula comprising about1,052 lbs. of No. 9 stone, 1,933 lbs. of No. 14 sand; 752 lbs. of highearly cement, 23 ounces of the above-identified water dispersing agent,and 40 gallons of water.

After formation of the slab 14 in the mold, curing may be furtheraccelerated by the use of cover members 276 removably positioned on thetop rails 32 and 34 of the side mold elements 28 and 30, and extendingover the slab l4 and enclosing the mold cavity, cover members 276 havingsuitable electrical heating elements 278 therein.

What is claimed is:

1. Apparatus for forming a cored cementitious slab comprising a mold,said mold having spaced-apart side elements for forming the sides of aslab and a bottom element having an upwardly facing surface for formingthe bottom surface of a slab, means for moving said side elementsrelative to said bottom element between a first position in which saidside elements extend upwardly from said surface of said bottom elementand define a mold cavity therewith, and a second position in which saidside elements are substantially removed from cooperative relationshipwith said bottom surface thereby to eliminate said mold cavity, meansfor progressively laying a layer of cementitious material in said mold,said laying means including means for receiving said material inrelatively fluid form and depositing the same in said mold, means formoving said laying means relative to said mold in one direction, aplurality of spaced-apart and parallel mandrels disposed in said moldand under said depositing means, said mandrels being elongated in saiddirection, said mandrels having ends disposed on opposite sides of saiddepositing means, means for attaching one end of said mandrels to saidlaying means whereby said mandrels move with said depositing means, andmeans for paying out reinforcing material over said mandrels as-saidmovement between said laying means and mold progresses.

2. Apparatus for forming a cored cementitious slab comprising anelongated mold having opposite ends, means for progressively laying alayer of cementitious material in said mold, said laying means includingmeans for receiving said material in relatively fluid form anddepositing the same in said mold, means for moving said laying meansrelative to said mold in the direction of elongation thereof toward onemold end and away from the other mold end, a plurality of spacedapartand parallel mandrels disposed in said mold and under said depositingmeans, said mandrels being elongated in the direction of said movement,said mandrels having ends disposed on opposite sides of said depositingmeans, means for attaching one end of said mandrels to said laying meanswhereby said mandrels move with said depositing means, an elongatedlength of mesh material having a free end, said free end being attachedto said mold adjacent to said other end thereof, said laying meansincluding a reel of said mesh material rotatably mounted on said layingmeans between said depositing means and said other mold end, means forrestraining the rotation of said reel, and means engaging said meshmaterial for urging said mesh material against said mandrels as saidmovement between said laying means and mold progresses.

3. The apparatus of claim 2 wherein said mold is stationary and includesspaced parallel side elements for forming said sides of said slab, and abottom element for forming said bottom surface, said moving meansincluding means for supporting said laying means adjacent said sideelements of said mold.

4. The apparatus of claim 1 further comprising means for impartingmotion to said mandrels.

5. The apparatus of claim 1 wherein said mandrels are respectivelyhollow and have liquid therein to maintain said mandrels in said layer.

6. The apparatus of claim 1 further comprising means for heating saidmandrels.

7. The apparatus of claim 2 wherein said laying means includes secondmeans disposed over said mold and said mandrels and between said reeland said other mold end for receiving cementitious material inrelatively fluid form and depositing a second layer thereof in said moldover said first-named layer and said mesh material.

8. Apparatus for forming a cored cementitious slab comprising anelongated mold for forming the parallel opposite sides and the bottomsurface of said slab; and means for progressively laying a layer ofcementitious material in said mold including means disposed above saidmold for receiving said material in relatively fluid form and depositingthe same in said mold, means for relatively longitudinally moving saidlaying means with respect to said mold in the direction of elongationthereof, a plurality of elongated mandrels disposed in said mold in aspaced, parallel relationship and extending in the direction of saidrelative movement for forming longitudinally extending core openings insaid slab, said mandrels having spaced opposite ends and having portionsintermediate said ends disposed under said depositing means, means forattaching the leading ends of said mandrels to said laying means therebyrelatively moving said mandrels with said depositing means, said layingmeans including second means disposed over said mold and said mandrelsfor receiving cementitious material in relatively fluid form anddepositing a second layer thereof in said mold over said first-namedlayer, said laying means including means cooperating with said firstlayer for supporting said second layer, said second layer ofcementitious material being deposited over said supporting means, saidmold having spaced opposite ends, said direction of relative movementbeing toward one mold end and away from the other, said supporting meansbeing an elongated length of mesh material having a free end, said freeend being attached to said mold adjacent said other end thereof, meansfor paying out said mesh material in response to movement of said layingmeans, said paying out means including a reel rotatably mounted on saidlaying means between said first-named and second depositing means foraccommodating a supply of said mesh material, and means for tensioningsaid mesh material as said relative movement progresses.

9. Apparatus for forming a cored cementitious slab comprising anelongated mold for forming the parallel opposite sides and the bottomsurface of said slab, and means for progressively laying a layer ofcementitious material in said mold including means disposed above saidmold for receiving said material in relatively fluid form and depositingthe same in said mold, means for relatively longitudinally moving saidlaying means with respect to said mold in the direction of elongationthereof, a plurality of elongated mandrels disposed in said mold in aspaced, parallel relationship and extending in the direction of saidrelative movement for forming longitudinally extending core openings insaid slab, said mandrels having spaced opposite ends and having portionsintermediate said ends disposed under said depositing means, means forattaching the leading ends of said mandrels to said laying means therebyrelatively moving said mandrels with said depositing means, said moldbeing stationary and having spaced opposite ends, said direction ofrelative movement being toward one mold end and away from the other,said laying means including a frame, said moving means including wheelsfor movably supporting said frame adjacent to said mold, each of saidmandrels having a longitudinally extending axis, said attaching meansincluding means mounted on said frame for supporting said leading endsof said mandrels for rotational movement about their respective axes,and means for imparting limited oscillatory movement to said mandrelsabout their respective axes, the trailing ends of said mandrels whichface toward said other mold end being unsupported by said frame andprojecting substantially beyond the same, said depositing meansincluding a first hopper supported on said frame, said first hopperhaving an auger therein and extending transversely across said mold,said first hopper being disposed to deposit said layer to a levelgenerally even with the tops of said mandrels, means for vibrating saidlayer, an elongated length of mesh material having a free end, said freeend being attached to said mold adjacent said other end thereof, a reelrotatably mounted on said frame for accommodating said mesh material andpaying out the same over said mandrels and layer as said relativemovement progresses, means for tensioning said mesh material as it ispayed out, means for pressing said mesh 5.1.0 material against saidmandrels and layer, second depositing means including a second hoppermounted on said frame, said second hopper having an auger therein andextending transversely across said mold for receiving cementitiousmaterial and depositing a second layer thereof in said mold over saidfirst-named layer and mesh material.

10. The apparatus of claim 1 further comprising a cover member forremovably covering said mold with said slab therein, and means forheating said cover member for accelerating the curing of said slab.

11. The apparatus of claim 1 wherein said mold includes a base memberfor forming said bottom surface, and further comprising means forheating said base member for accelerating the curing of said slab.

12. The apparatus of claim 1 wherein said laying means includ'es aframe, said depositing means being supported on said frame, saidmandrels being attached to said frame, and said frame being supported onopposite sides of and adjacent to said mold.

13. The apparatus of claim 1 wherein each of said mandrels has alongitudinal axis extending between said ends thereof, and furthercomprising means for imparting limited rotary oscillatory movement tosaid mandrels about their respective axes.

14. The apparatus of claim l further comprising means respectivelydisposed between said mandrels for vibrating the material deposited insaid mold.

15. Apparatus for forming a cored cementitious slab for use with a moldhaving spaced apart side elements for forming the sides of the slab anda bottom element with an upwardly facing surface for forming the bottomsurface of the slab comprising means for progressively laying a layer ofcementitious material in a mold, said laying means including means forreceiving said material in relatively fluid form and depositing the samein the mold, means for moving said laying means relative to the mold, aplurality of spaced-apart mandrels which are to be placed in the moldbetween the side elements thereof, said mandrels being beneath saiddepositing means, said mandrels being attached to said laying meanswhereby said mandrels move with said depositing means, and means forpaying out a cementitious material supporting material over saidmandrels, and means for urging said supporting material against saidmandrels.

1. Apparatus for forming a cored cementitious slab comprising a mold,said mold having spaced-apart side elements for forming the sides of aslab and a bottom element having an upwardly facing surface for formingthe bottom surface of a slab, means for moving said side elementsrelative to said bottom element between a first position in which saidside elements extend upwardly from said surface of said bottom elementand define a mold cavity therewith, and a second position in which saidside elements are substantially removed from cooperative relationshipwith said bottom surface thereby to eliminate said mold cavity, meansfor progressively laying a layer of cementitious material in said mold,said laying means including means for receiving said material inrelatively fluid form and depositing the same in said mold, means formoving said laying means relative to said mold in one direction, aplurality of spaced-apart and parallel mandrels disposed in said moldand under said depositing means, said mandrels being elongated in saiddirection, said mandrels having ends disposed on opposite sides of saiddepositing means, means for attaching one end of said mandrels to saidlaying means whereby said mandrels move with said depositing means, andmeans for paying out reinforcing material over said mandrels as saidmovement between said laying means and mold progresses.
 2. Apparatus forforming a cored cementitious slab comprising an elongated mold havingopposite ends, means for progressively laying a layer of cementitiousmaterial in said mold, said laying means including means for receivingsaid material in relatively fluid form and depositing the same in saidmold, means for moving said laying means relative to said mold in thedirection of elongation thereof toward one mold end and away from theother mold end, a plurality of spaced-apart and parallel mandrelsdisposed in said mold and under said depositing means, said mandrelsbeing elongated in the direction of said movement, said mandrels havingends disposed on opposite sides of said depositing means, means forattaching one end of said mandrels to said laying means whereby saidmandrels move with said depositing means, an elongated length of meshmaterial having a free end, said free end being attached to said moldadjacent to said other end thereof, said laying means including a reelof said mesh material rotatably mounted on said laying means betweensaid depositing means and said other mold end, means for restraining therotation of said reel, and means engaging said mesh material for urgingsaid mesh material against said mandrels as said movement between saidlaying means and mold progresses.
 3. The apparatus of claim 2 whereinsaid mold is stationary and includes spaced parallel side elements forforming said sides of said slab, and a bottom element for forming saidbottom surface, said moving means including means for supporting saidlaying means adjacent said side elements of said mold.
 4. The apparatusof claim 1 further comprising means for imparting motion to saidmandrels.
 5. The apparatus of claim 1 wherein said mandrels arerespectively hollow and have liquid therein to maintain said mandrels insaid layer.
 6. The apparatus of claim 1 further comprising means forheating said mandrels.
 7. The apparatus of claim 2 wherein said layingmeans includes second means disposed over said mold and said mandrelsand between said reel and said other mold end for receiving cementitiousmaterial in relatively fluid form and depositing a second layer thereofin said mold over said first-named layer and said mesh material. 8.Apparatus for forming a cored cementitious slab comprising an elongatedmold for forming the parallel opposite sides and the bottom surface ofsaid slab; and means for progressively laying a layer of cementitiousmaterial in said mold including means disposed above said mold forreceiving said material in relatively fluid form and depositing the samein said mold, means for relatively longitudinally moving said layingmeans with respect to said mold in the direction of elongation thereof,a plurality of elongated mandrels disposed in said mold in a spaced,parallel relationship and extending in the direction of said relativemovement for forming longitudinally extending core openings in saidslab, said mandrels having spaced opposite ends and having portionsintermediate said ends disposed under said depositing means, means forattaching the leading ends of said mandrels to said laying means therebyrelatively moving said mandrels with said depositing means, said layingmeans including second means disposed over said mold and said mandrelsfor receiving cementitious material in relatively fluid form anddepositing a second layer thereof in said mold over said first-namedlayer, said laying means including means cooperating with said firstlayer for supporting said second layer, said second layer ofcementitious material being deposited over said supporting means, saidmold having spaced opposite ends, said direction of relative movementbeing toward one mold end and away from the other, said supporting meansbeing an elongated length of mesh material having a free end, said freeend being attached to said mold adjacent said other end thereof, meansfor paying out said mesh material in response to movement of said layingmeans, said paying out means including a reel rotatably mounted on saidlaying means between said first-named and second depositing means foraccommodating a supply of said mesh material, and means for tensioningsaid mesh material as said relative movement progresses.
 9. Apparatusfor forming a cored cementitious slab comprising an elongated mold forforming the parallel opposite sides and the bottom surface of said slab,and means for progressively laying a layer of cementitious material insaid mold including means disposed above said mold for receiving saidmaterial in relatively fluid form and depositing the same in said mold,means for relatively longitudinally moving said laying means withrespect to said mold in the direction of elongation thereof, a pluralityof elongated mandrels disposed in said mold in a spaced, parallelrelationship and extending in the direction of said relative movementfor forming longitudinally extending core openings in said slab, saidmandrels having spaced opposite ends and having portions intermediatesaid ends disposed under said depositing means, means for attaching theleading ends of said mandrels to said laying means thereby relativelymoving said mandrels with said depositing means, said mold beingstationary and having spaced opposite ends, said direction of relativemovement being toward one mold end and away from the other, said layingmeans including a frame, said moving means including wheels for movablysupporting said frame adjacent to said mold, each of said mandrelshaving a longitudinally extending axis, said attaching means includingmeans mounted on said frame for supporting said leading ends of saidmandrels for rotational movement about their respective axes, and meansfor imparting limited oscillatory movement to said mandrels about theirrespective axes, the trailing ends of said mandrels which face towardsaid other mold end being unsupported by said frame and projectingsubstantially beyond the same, said depositing means including a firsthopper supported on said frame, said first hopper having an augertherein and extending transversely across said mold, said first hopperbeing disposed to deposit said layer to a level generally even with thetops of said mandrels, means for vibrating said layer, an elongatedlength of mesh material having a free end, said free end being attachedto said mold adjacent said other end thereof, a reel rotatably mountedon said frame for accommodating said mesh material and paying out thesame over said mandrels and layer as said relative movement progresses,means for tensioning said mesh material as it is payed out, means forpressing said mesh material against said mandrels and layer, seconddepositing means including a second hopper mounted on said frame, saidsecond hopper having an auger therein and extending transversely acrosssaid mold for receiving cementitious material and depositing a secondlayer thereof in said mold over said first-named layer and meshmaterial.
 10. The apparatus of claim 1 further comprising a cover memberfor removably covering said mold with said slab therein, and means forheating said cover member for accelerating the curing of said slab. 11.The apparatus of claim 1 wherein said mold includes a base member forforming said bottom surface, and further comprising means for heatingsaid base member for accelerating the curing of said slab.
 12. Theapparatus of claim 1 wherein said laying means includes a frame, saiddepositing means being supported on said frame, said mandrels beingattached to said frame, and said frame being supported on opposite sidesof and adjacent to said mold.
 13. The apparatus of claim 1 wherein eachof said mandrels has a longitudinal axis extending between said endsthereof, and further comprising means for imparting limited rotaryoscillatory movement to said mandrels about their respective axes. 14.The apparatus of claim 1 further comprising means respectively disposedbetween said mandrels for vibrating the material deposited in said mold.15. Apparatus for forming a cored cementitious slab for use with a moldhaving spaced apart side elements for forming the sides of the slab anda bottom element with an upwardly facing surface for forming the bottomsurface of the slab comprising means for progressively laying a layer ofcementitious material in a mold, said laying means including means forreceiving said material in relatively fluid form and depositing the samein the mold, means for moving said laying means relative to the mold, aplurality of spaced-apart mandrels which are to be placed in the moldbetween the side elements thereof, said mandrels being beneath saiddepositing means, said mandrels being attached to said laying meanswhereby said mandrels move with said depositing means, and means forpaying out a cementitious material supporting material over saidmandrels, and means for urging said supporting material against saidmandrels.